fix scheduling, threading and movement bugs

scheduling:
- cursor mover created a new java.util.timer for every movement and never
  cancelled it, leaking a live thread roughly every 10 seconds; timers are
  replaced by a single shared scheduledexecutorservice with daemon threads,
  shut down when the automation stops.

clicks:
- the double click sequence used thread.sleep() inside a timer task, blocking
  the scheduler thread; it is now scheduled as one-shot actions on the shared
  scheduler, with the same pacing as before.
- stopping the automation now also cancels in-flight movements and pending
  clicks, instead of letting them run to completion.

movement math:
- when the destination shared one coordinate with the starting position, the
  step on the other axis was computed as length/0 = infinity, and the stop
  condition checked one axis with || instead of &&, so a movement could stop
  (and click) before reaching its destination. steps are now guarded and the
  movement stops only when both axes have converged.

ui and lifecycle:
- the app could not be closed: closing the window only hid it, and ESC
  unregistered the hotkey without exiting. the window now exits cleanly on
  close, stopping the automation and unregistering the native hook.
- toggleRunning() was called from the jnativehook thread and touched swing
  components off the EDT; UI updates are now marshalled to the EDT.
- the hotkey thrashed: key repeats re-fired the toggle while ctrl+alt was
  held, and any other key pressed with the combo held toggled it too. it now
  fires exactly once, when the combo is completed.

away-detection (CursorMoveListener) stays intentionally unscheduled: it cannot
tell the user's movements apart from the app's own, and will be reworked in a
future iteration.

src/main/java/wtf/beatrice/autosqueal/controls/CursorMover.java

@@ -7,66 +7,61 @@ import wtf.beatrice.autosqueal.util.RunnerUtil;
 import java.awt.*;
 import java.security.SecureRandom;
 import java.util.Random;
-import java.util.Timer;
-import java.util.TimerTask;
+import java.util.concurrent.ScheduledExecutorService;
 
-public class CursorMover extends TimerTask
+/**
+ * Periodically starts a new movement of the mouse cursor to a random position,
+ * or to the top-right corner of the screen for a double click.
+ *
+ * The movement itself is executed by a {@link SingleStepMovementTask}, which
+ * re-schedules itself on the shared scheduler until it reaches its destination.
+ */
+public class CursorMover implements Runnable
 {
-
     private static final Logger LOGGER = LogManager.getLogger(CursorMover.class);
-    private final Random random;
 
     private static final int LOOPS_BEFORE_CLICK = 5;
 
+    private final Random random = new SecureRandom();
+    private final ScheduledExecutorService scheduler;
+
     private int iteration = 0;
 
-    public CursorMover() {
-        random = new SecureRandom();
+    public CursorMover(ScheduledExecutorService scheduler) {
+        this.scheduler = scheduler;
     }
 
     @Override
     public void run() {
 
-        int currentX = MouseInfo.getPointerInfo().getLocation().x;
-        int currentY = MouseInfo.getPointerInfo().getLocation().y;
-
-        LOGGER.info("Starting coordinates: {}, {}", currentX, currentY);
+        Point location = MouseInfo.getPointerInfo().getLocation();
+        LOGGER.info("Starting coordinates: {}, {}", location.x, location.y);
 
         int destX;
         int destY;
-
-        SingleStepMovementTask singleStepMovementTask;
+        boolean click;
 
         if (iteration == LOOPS_BEFORE_CLICK) {
             destX = RunnerUtil.SCREEN_WIDTH - 5;
             destY = 5;
-
-            try {
-                singleStepMovementTask = new SingleStepMovementTask(destX, destY, true);
-            } catch (AWTException e) {
-                LOGGER.error(e);
-                return;
-            }
+            click = true;
 
             iteration = 0;
         } else {
             destX = random.nextInt(RunnerUtil.SCREEN_WIDTH);
             destY = random.nextInt(RunnerUtil.SCREEN_HEIGHT);
-
-            try {
-                singleStepMovementTask = new SingleStepMovementTask(destX, destY, false);
-            } catch (AWTException e) {
-                LOGGER.error(e);
-                return;
-            }
+            click = false;
 
             iteration++;
         }
 
         LOGGER.info("Destination coordinates: {}, {}", destX, destY);
 
-        Timer timer = new Timer();
-        timer.schedule(singleStepMovementTask, 0L, 2L);
-
+        try {
+            SingleStepMovementTask movement = new SingleStepMovementTask(scheduler, destX, destY, click);
+            scheduler.execute(movement);
+        } catch (AWTException ex) {
+            LOGGER.error("Could not start movement task", ex);
+        }
     }
-}
+}